Manufacture of mass production molded devices, such as contact lenses, is typically conducted by cast-molding of a reactive composition (or a lens-forming formulation or composition) in a mold comprising a first (e.g., female) mold half having a first molding surface defining one of the two opposite surfaces of a contact lens and a second (e.g., male) mold half having a second molding surface defining the other surface of the contact lens. A lens (device) forming composition (formulation) is dispensed into the female mold half followed by closing the mold by attaching the male mold half onto the female mold. The cavity between the first and second molding surfaces of the mold in closed state defines the form of the contact lens to be molded. In order to transform the lens forming formulation within the mold pair into a contact lens said formulation is polymerized or crosslinked.
Thereafter the mold halves are separated and the formed contact lens is demolded. The contact lens is further processed, and the mold is dispensed, or in the case of re-usable molds, cleaned and dried, and used for manufacture of further contact lenses. A process as described hereinbefore is generally independent of the mold material used or the lens forming formulation used. To meet the needs of as many patients as desirable it is important to manufacture contact lenses having a variety of different parameters or parameter combinations. Examples for such parameters are the power of a contact lens, or information about the angle of a toric axis in case of toric contact lenses (i.e., orientation marks), inversion marks for facilitating lens handlings, or manufacturing data or shelf life data or expiry information relating to a contact lens.
In order to avoid any mixup or confusion after manufacture of a contact lens it is most desirable to connect the respective parameters or data with each individual contact lens instead of simply printing said parameters only on primary or secondary packages. A convenient method of marking a contact lens directly with such parameters consists of transferring a symbol or a pattern from a lens mold to a contact lens.
In order to achieve this it is known to create a symbol to the surface of a mold, either as an indentation on the mold or as an elevation on the mold. Said indentation or elevation is then reproduced on the contact lens during the molding process such that an indentation in the mold results in a corresponding elevation on the contact lens while an elevation in the mold results in a corresponding indentation on the contact lens.
The indentation or elevation on the mold in those known processes for applying a symbol to a contact lens is a fixed and permanent element of the mold. It cannot be changed or varied. Re-usable molds of this type having a permanent indentation or elevation, therefore, can be used only for the manufacture of the specific type of contact lens described by said permanent indentation or elevation. This fact requires a manufacturer of contact lenses to have a large stock of molds carrying indentations or elevations needed for the many different types of parameters which are to be applied to a contact lens.
Another problem related to molds having permanent indentations or elevations exists in the area of accumulation of debris or other undesired material. This may have the effect of such material masking the original indentation or elevation resulting in poor visibility/readability of the intended symbol. In the alternative, the debris or other undesired material may be transferred to the contact lens during the molding process which is also an undesired effect.
In view of the disadvantages shortly addressed hereinbefore there is still a need to develop an improved process for marking a contact lens on its surface with a symbol avoiding or overcoming said disadvantages. Such a process is disclosed herein in the specification and claims of this patent document.